1. Field of the Invention
The present invention relates to a battery control system and a battery control method which dispose, as a hierarchical structure, control devices that control batteries.
2. Description of the Related Art
A technology of charging a battery with power generated by utilizing natural energy and with power from a system is getting attention. A battery control system realized by such a technology has, as shown in FIG. 9, slave control devices 93 controlling a battery and connected in series or in parallel as a group, and a master control device 92 comprehensively controls such a group of the slave control devices 93. Moreover, a whole group of the plurality of master control devices 92 is managed by a battery-system managing device 91, and thus a large-capacity battery is realized. In the battery control system having master and slave control systems as a hierarchical structure, the battery-system managing device 91 transmits a control signal to instruct charging, discharging, etc., of the battery to each slave control device 93 through the master control device 92, and manages a status of a communication line for transmitting/receiving the control signal and the operation status of the control device itself (see JP 2000-358330 A).
According to the conventional battery control system shown in FIG. 9, however, when the master control device 92 suffers a fault like a breakdown, a communication with the slave control devices 93 managed by that master control device 92 is disabled, and a battery charging/discharging control is also disabled even if the battery controlled by that master and slave control devices 92 and 93 is in a normal condition.
For example, in the example case shown in FIG. 9, when a fault occurs at the master control device 92 (92A), the slave control devices 93 ((1) to (8)) under the control of such a master control device become unable to control the battery since a communication is disabled between the master control device 92 and each slave control device 93.
The present invention has been made in view of such a circumstance, and it is an object of the present invention to provide a battery control system and a battery control method that can avoid uncontrollability of a battery by slave control devices when a master control device suffers a fault in a system which establishes a hierarchical structure of the master control system and the slave control systems and which transmits a control signal for controlling a battery.